Index center



J. HARLEY INDEX CENTER April 25, 1933.

Filed Sept; 22, 1931 3 Sheets-Sheet l April 25, 1933.

.1, HARLEY INDEX CENTER Filed Sept. 22, 1931 3 Sheets-Sheet 2 HH EH m H We April 25, 1933.

Filed Sept. 22, 1931 J. HARLEY INDEX CENTER 3 Sheets-Sheet 5 Patented Apr. 25, 1933 UNITED. S TES PROVIDENCE, RHODE IS AND PATENT OFFICE INDEX CENTER This invention relates to index centers, and more particularly relates to the indexing discs, the primary object of the invention being to enable the work to be turned throughout a greater range withoutchanging the disc. i

1 Index discs of common usage are nominally used for dividing a circle into a definite number of equal parts (not degrees and minutes) in the 'milling of teeth and gear wheels, and hexagonal and square milling of shafts. i

The method usually adopted for angular indexing is as follows: 7

Divide 5 10 by the total number of minutes tobe indexed. If the quotient is approximately equal tothe number of holes in any index circle available the angular movement is obtained by moving the crank one hole in this index circle; butif the quotient is not approximately equal, multiply it by any trial number which will givea product equal to the number of holes in an available index circle and move the, index crank as many holes as are indicated by thetrial number.- If the quotient of 540 divided by the total number ofminutes is greater than the number of; holes in any of the index circles, it is not possible to obtain the required movement for-the angle by simple indexing.

This shows that, only some of the angles in degrees and minutes, can be obtained accurately by simple indexing, and compound indexing, which would be more accurate, involves greater calculations on the part of the workmamand leads to errors.

The above method also shows that for different angles, different discs are often required, and it is only possible to turn the work through this angle and back to zero; therefore, it is not possible to turn the work accurately through a successionof angles in degrees and minutes in many cases. -If a change of disc is necessary it would be im: possible to place the second disc in thepsame position as thefirst one, due to theflindex crank not being opposite a hole. The present invention therefore aims [to provide a disk which overcomes the objection supra and in which when milling at an off angle is required the templets which are made to a protractor and which do not give the same degree of accuracy and are more costly, are dispensed with.

- In the drawings Figure 1 is a vertical sectional view of an indexing center having the presentinvention applied thereto;

Figure 2 is a plan view of one form indexing disc; r t

Figure 3 isan edge view thereof;

Figure 4; is a plan view of the reverse side of Figure 2; r

. Figure 5 isa plan view. of the modified form of the invention wherein the holes are drilled completely through Figure 6 is an enlarged section on the line 6-6 of Figure 2 and Figure 7 is a similar section on the line 77 of Figure 2.

Figure 1 of the drawings illustrates a milling machine having a worm shaft 1 operated by an arm 2 and a handle 3, the handle having the usual spring pressed'releasable pin 4 which engages in a selected one of the perforations of the indexing disc 5. The worm 6 of the shaft 1 meshes with a worm gear having ratio of/lO to 1 to the gear 7 which in turn operates the spindle 8 upon which thework is supported. A releasable latch or zero pin 9 engages in perforations upon the rear of the disc 5 and at' the bottom of the latter. The invention resides particularly in the location of the openings for receiving the pin 9.

In Figure 2 it will be seen that there are six series of circumferentialopenings 10, 11, 12, 13, 1 1, and 15; the series 10 being composed of 20 holes, the series 11 composed of 19holes, the series 12 composed of 18 holes, the series 13 composed of 17holes, the series 1 1 composed of 16 holes, and the series 15 composed of 15 holes, the number of holes being indicated as shown at'16, all of the holes in question appearing'on "the one side face of the disc. Referring to Figure ,5 it will be seen that the standard series of holes 19 are 18 in number. The standard series of holes must be 9 or anymultiple of 9, by reason of the action of the worm 6 on the JOHN HARLEY, or GLASGOW, SCOTLAND, AssmNo'n 'ro BROWN & SHARPE MFG. 00., or s gear 7 operating the shaft 8 which carries the work, the worm being geared to the shaft as of one (1) to forty (40) as shown in Figure 1.

Referring to Figures 4 and 6 it will be seen that the disc is provided with holes 17 certain of which extend but partly through the disc thereby to provide cranking or movement of the disc in a clockwise movement. In Figure 3 it will be noted that the peripheral edge of the plate is marked to identify the 29 holes which constitute the circular series of holes 17 as shown at 18.

The above form of'the invention is particularly for use with angular indexing and it will be noted that the 20 holes in the outer circle or series 10 of the standard 20 hole disc extend but slightly more than half way through the disc and that the differential index holes are drilled from the opposite side of the disc, that is on the side next the zero pin in the dividing head. Referring to Figure 5 of the drawings it will be noted that the disc 1a is provided with a series of holes 19 which are marked from 1 to 18 and which are the standard holes, while a sec- 0nd series of holes 20 constituting a total of 29 are off-set circumferentially from the standard 18 holes by an amount which is equivalent to 1, 2, 3, etc., minutes on the work. The disc is marked on both sides to accommodate cranking in either a clockwise or counter clockwise direction, and the indexing for degrees and half degrees is the same as the present on all dividing heads, the addition of minutes from 1 to 29 being the only difference.

In use of the invention for cranking in a clockwise direction and referring to Figure 5: Ewample 1 It is desired to rotate the work through and 3 13 minutes.

See that zero pin and crank pin are inserted in their respective zero holes.

Withdraw crank pin and swing crank through 3 i.e. 6/18 and insert crank pin.

Swing register arm 21 around against crank pin to approximately locate its position.

Withdraw crank pin and Zero pin. Turn index plate around andinsert zero pin in 13 minute hole.

Swing crank in aclockwise direction until crank pin enters the first hole. This gives the desired angle to the work.

Example 52 It is desired to rotate the work through a further angle of say 3 degrees, 14 minutes, starting where we left off in the first example.

Swing crank through 3 degrees from present position.

Swing register arm against crank pin,

Withdraw crank pin and zero pin.

(It is now necessary to add the minutes only, i. e. 13+14:=27.)

Turn index plate and insert zero pin in 27 minute hole.

Again turn crank until crank pin enters the first hole in a clockwise direction. The work has now been rotated through a total an le of 6 degrees 27 minutes:

IIf when rotating the work through several angles,the addition of the last number of minutes comes to or 30, the zero pin should be inserted in the zero hole, and the crank turnedto the first hole in a clockwise direction as before.)

Example 3 The angle required is say 1 degree 49 minutes.

Swing crank through 1% degrees and add 19 minutes as before.

It will be seen that in each form of the invention there occurs a standard circumferential series of 18 holes and a second series of holes off-set circumferentia-lly from the standard series by an amount which is equivalent to the number of minutes on the work. In the form of the invention shown in Figures 2, 3, and 4, the only difierence over the form shown in Figure 5, is that the former is for use with angular indexing.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An index centering disc, comprising an index plate provided with a standard series of holes marked from 1 to 18 and a second circular series of holes constituting a total of 29 which are off-set circumferentially from the first named series by an amount which is equivalent to the number of minutes on the work, the plate having markings on both sides to provide for cranking in a clockwise or counter clockwise movement or direction, the periphery of the plate having appropriately designated indicia thereon and spaced to correspond with the series of 29 holes to indicate the number of minutes on the work. I

2. An index centering disc, comprising an index plate provided with a standard series of holes marked from 1 to 18 and a second circular series of holes constituting a total of 29 which are off-set circumferentially from the first named series by an amount which is equivalent to the number of minutes on the work, the periphery of the plate having appropriately designated indicia thereon and spaced to correspond with the series of 29 holes to indicate the number of minutes on the work.

3. An index centering disc, comprising an index plate provided with a standard series of spaced holes, and a second circular series of spaced holes which latter are offset circumferentially from the first named series by an amount which is equivalent to the number of minutes on the work, said last named series of holes extendin into the plate a distance less than one-hal the thickness of the latter, and said plate having markings on both sides to provide for cranking in a clockwise or counter clockwise direction.

0 4. An index centerin disc, comprising an index plate provided with a standard series of spaced holes, and a second circular series of spaced holes which are ofiset circumferentially from the first named series by an amount which is equivalent to the number of minutes on the work, said last named series of holes extending into the plate a distance less than one-half the thickness of the latter, and the periphery of said plate having appropriately designated indicia thereon to correspond to the last named series of holes whereby to indicate the minutes on the work.

In testimony whereof I have signed my name to this specification.

JOHN HARLEY. 

